Discharge tube stabilizer system



Feb. 6, 1934.

DISCHARGE TUBE STAB'ILIZER sYs'rEu Filed Jan. 19, 1931 Ewe/2%? M. MORRISON 1,945,751

Patented Feb. 6, 1934 UNITED STATES 1,945,751 DISCHARGE TUBE STABILIZER SYSTEM Montford Morrison, Montclair, N 3., assignor to Westinghouse X-Ray Company, Inc., a corporation of Delaware Application January 19, 1931. Serial No. 509,572

9 Claims.

My invention relates to thermionic discharge tubes and more particularly to a system for stabilizing the discharge current flowing therethrough.

In thermionic discharge tubes the operation is dependent upon the flow of electrons from a thermionic cathode and the potential applied between the anode and cathode of the tube. In order to maintain the discharge current of the tube constant the electron emissivity must be maintained constant otherwise the discharge current will vary with variations in electron emissivity.

Numerous factors are controlling in a device of this character, such for example, as the pressure within the tube, the potential applied between the electrodes, and the temperature to which the cathode is heated and variations in any of these factors will cause a variation in the discharge current of the tube. As the usual practice is to supply the energy for the tube, and the filament heating energy from a common source of commercial potential subject to line fluctuations, an additional condition occurs which, if not in some manner compensated for,wil1 cause variations in the discharge current.

Various devices for maintaining the discharge current constant in a thermionic discharge tube, are known in the art, but these devices have consisted mainly of moving elements which are very objectionable. Some devices, however, have been utilized which consist of elements operable by electric phenomenon but these are readily susceptible to wear or break-down and must therefore be frequently replaced.

It is accordingly an object of my invention to provide a stabilizer system for thermionic discharge tubes in which all moving parts aredispensed with and which is entirely electrically responsive to conditions within the circuit.

Another object of my invention is the provision of a stabilizer system for a thermionic discharge tube circuit that is electrically responsive to conditions in the circuit and which is constructed to form an integral part of the apparatus.

Another object of my invention is the provision of a stabilizer system for a discharge tube in which the electrically responsive device forms an integral part of the apparatus and is not subjet to wear or break-down usually attendant such devices.

Still further objects of my invention will become apparent to those skilled in the art by reference to the accompanying drawing wherein the single figure is a diagrammatic representation of a discharge tube and a circuit therefor utilizing my invention.

Referring now to the drawing in detail I have shown a high-tension transformer 2 provided with the usual primary winding 3 and secondary winding 4. An auto-transformer 5 is connected to the primary winding 3, by means of conductors 6 and "Z, and a suitableswitch 8 is disposed in the conductor 7 for the purpose of connecting and disconnecting the primary winding 3 to the autotransformer. A pair of conductors 9 and 10 in turn connect the auto-transformer to a suitable source of commercial alternating potential such as a generator 12. r r

The secondary winding 4 is connected by means 79 of a conductor 13 to a terminal 14 of a suitable rectifying device 15 herein shown as a mechanical rectifying device of the sphere and toroid type shown and described in my Patent No. 1,466,541 of August 28, 1923. Another conductor Z5 16 connects the other end of the secondary winding 4 to a similar terminal 17 of the rectifying device. A terminal 18 of the rectifying device 15 is connected, by means of a conductor 19, to the anode of an X-ray tube 20 which is encased Si) in a suitable ray opaque housing 22;

The filamentary cathode of the X-ray tube 20 is electrically associated with the rectifying device 15 by means of a conductor 25 which extends from the cathode to a terminal 24 of the rectifying device 15. The cathode is arranged to be heated to an electron emitting temperature by means of a low tension transformer 26, the secondary winding 27 of which is connected to the conductor 25 by means of a conductor 28 and to the cathode of the X-ray tube 20 by means of a conductor 29. The primary winding 30 of the low tension transformer 26 receives energization from the common source of potential such as the generator 12 by means of conductors 32 and 33. A constant potential device 34 of well known design may be interposed in the conductor 33 if desired for maintaining the potential supplied to the primary winding 30 at a constant value.

An auxiliary winding 35 of a few turns is Wound upon the core with the secondary winding 4 of the high-tension transformer 2. A similar auxiliary winding 36, having a greater number of turns than the winding 35, is wound upon the core of the primary winding 30 of the low-tension transformer 26, and a pair of conductors 371and 38 connect these two auxiliary windings in series.

The auxiliary winding 36 is differentially wound with respect to the primary winding 30 or in other words it is wound upon the core of the transformer 26 in a direction opposite to that of the primary winding 30 and produces an opposing magnetic field or bucking effect for a purpose now about to be described.

The operation of my system'is as follows: Assuming it is desired to energize the X-ray tube 20 the switch 8 is closed allowing energy to flow from the auto-transformer 2 through the conductors 6 and 7. At the same time energy will flow from the common source 12 to the primary winding 30 of the low-tension transformer 26, through the conductors 32 and 33 and the constant potential device 34. The energization of the primary windings of the respective transformers likewise energize the secondary windings of these transformers. Electrical energy will therefore flow from the secondary winding 27 through the conductors 28 and 29 and thus heat the cathode of the X-ray tube 20 to an electron emitting temperature.

Energy will likewise flow from the secondary winding 4, through the conductor13 to the terminal 14, thence through the rectifying device 15 to the terminal 24, through conductor 25 and X-ray tube 20 and by means of conductor 19 to the terminal 18, again through the rectifying device 15 to the terminal 1''! and thence back to the secondary winding 4, through the conductor 16. The energy will flow through the circuit as just described during one-half the alternating current wave and during the other half of the wave, due to the rotation of the rectifying device which is synchronously driven as described in my aforementioned patent, it will traverse substantially the same circuit differing only in the establishment of a different connection in the rectifying device. 7

As the rectifying device rotates one quarter of a revolution the current will flow from the terminal 17 to the terminal 24, then through the circuit as previously traced to the terminal 18, thence to the terminal 14 and back to secondary winding 4. Y I

The energization of the secondary winding 4 by the primary winding 3 likewise energizes the auxiliary winding 35 which in turn energizes the auxiliary winding 36 in the low-tension transformer 26. As the temperature of the cathode is maintained by permitting a predetermined amount of current to flow from the low tension transformer and a predetermined potential is applied between the electrodes of the X-ray tube the discharge current will amount to a certain value. Assuming now that due to line fluctuations in the source 12 the current increases; an increase in current will then occur in the primary windings 3 and 30 which would be induced in the respective secondary windings 4 and 2'7. This increase in current would, therefore, increase the discharge current flowing through the tube 20 and also the electron emissivity of the cathode but due to the increased current in the primary winding 3 being also induced in the auxiliary winding 35, which is in turn transmitted through conductors 3'7 and 38, to the differential auxili ary winding 36 a bucking effect is produced in the primary winding 30 which reduces the current induced in the secondary winding 27. This decrease of current necessarily reduces the temperature of the cathode and its electron emissivity which, therefore, prohibits an increase in the discharge current with an increase of our- 7 rent in the source.

Should for any reason a variation occur in any other of the aforementioned factors, such for example, as a variation of pressure within the tube which would decrease the discharge current, this decrease will likewise occur in the respective auxiliary windings 35 and 36. A decrease in the winding 36 would permit the primary winding 30 to induce an increase of current in the secondary winding 27 and increase the temperature of the cathode and its electron emissivity thus again stabilizing the discharge current through the tube.

It can thus be readily seen that I have provided a stabilizer system for a thermionic discharge tube that is constructed as an integral part of the apparatus, which is entirely devoid of moving parts and is not subject to wear or break down usually attendant such devices.

Although I have shown and described one specific embodiment of my device I do not desire to be limited thereto as various other modifications of the same may be made without departing from the spirit and scope of the appended claims.

What is claimed is: r

1. In combination with a thermionic discharge tube provided with an elec ron emitting cathode and subject to variations in discharge current, a high-tension transformer for energizing said tube, a low-tension transformer for supplying heating energy to the cathode of said tube, a tertiary winding wound upon the core of said hightension transformer, a tertiary winding wound upon the core of said low-tension transformer and connected to said first mentioned tertiary winding whereby the current in one of said transformers is varied in accordance with the variaof current in the other of transformers for stabilizing the discharge current of said tube.

2. In combination with a thermionic discharge tube provided with an electron emitting cathode and subject to variations in discharge current, a hi h-tension transformer for energizing said tube, a low-tension transformer for supplying heating energy to the cathode of said tube, a tertiary winding wound upon the core with the secondary winding of said high-tension transformer, a tertiary winding wound upon the core with the primary winding of said low-tension transformer and connected to said first mentioned tertiary winding for simultaneously varying the current in one of said transformers in accordance with the current variations in the other of said transformers and stabilizing the discharge current of said tube.

3. In combination with a thermionic discharge tube provided with an electron emitting cathode and subject to variations in discharge current, a high-tension transformer for supplying electrical energy to said tube, a low-tension transformer for supplying heating energy to the cathode of said tube, a tertiary winding associated with the secondary winding of said high tension transformer and inductively coupled with the primary winding of said high-tension transformer, a tertiary winding differentially associated with the primary winding of said low-tension transformer and inductively coupled to the secondary winding of said low-tension transformer, said last mentioned tertiary winding being connected to said first mentioned tertiary winding for simultaneously varying the current in one of said transformers in accordance with the current variations in the other of said transformers and stabilizing the discharge current of said tube.

In combination with a thermionic discharge tube provided with an electron emitting cathode and subject to variations in discharge current, a

high-tension transformer for supplying electrical energy to said tube, a low-tension transformer for supplying heating energy to the cathode of said tube, a tertiary winding wound upon the core with the secondary winding of said high-tension transformer, a tertiary winding wound upon the core with the primary winding of said low-tension transformer, said last mentioned tertiary winding being differentially wound relative to the primary winding of said low tension transformer and connected to said first mentioned tertiary winding for increasing the temperature and electron emissivity of said cathode upon a decrease in the discharge current and for decreasing the temperature and electron emissivity of said cathode upon an increase in the discharge current to thereby maintain the discharge current of said tube constant.

5. In combination with a thermionic discharge tube provided with an electron emitting cathode and subject to variations in discharge'current, a high-tension transformer for supplying electrical energy to said tube, a low-tension transformer for supplying heating energy to the cathode of said tube, a tertiary winding wound upon the core with the secondary winding of said high-tension transformer, a tertiary winding wound upon the core with the primary winding of said low-tension transformer, said last mentioned tertiary winding being differentially wound relative to the primary winding of said low-tension transformer and connected to said first mentioned tertiary winding for varying the energy in one of said transformers conversely to variations in the other of said transformers to stabilize the discharge current in said tube.

6. In an electrical circuit the combination of a thermionic discharge device provided with an electron emitting cathode and subject to variations in discharge current, a high-tension transformer for supplying electrical energy to said device, a low-tension transformer for supplying heating currents to the cathode of said device, a tertiary winding wound upon the core of both of said transformers and connections therebetween whereby the temperature of said cathode is controlled in accordance with variations in the discharge current for maintaining the discharge current through said device constant.

'7. In an electrical circuit the combination of a thermionic discharge device provided with an electron emitting cathode and subject to variations in the discharge current, a high-tension transformer for supplying electrical energy to said device, a low-tension transformer for supplying heating currents to the cathode of said device, a tertiary winding wound upon the core with the secondary winding of said high-tension transformer, a tertiary winding differentially wound upon the core with the primary winding of said low-tension transformer and connected to said first mentioned tertiary winding whereby the discharge current is varied in accordance with variations of current in said low-tension transformer for maintaining the discharge current in said device constant.

8. In an electrical circuit the combination of a thermionic discharge device provided with an electron emitting cathode and subject torvariations in discharge current, a high tension transformer for supplying electrical energy to said device, a low-tension transformer for supplying heating currents to the cathode of said device, a tertiary winding wound upon the core with and inductively coupled to the secondary winding of said high-tension transformer, a tertiary winding wound upon the core with and inductively coupled to said low-tension transformer, said last mentioned tertiary winding being differentially wound relative to the primary winding of said low-tension transformer and connected to said first mentioned tertiary winding for varying the temperature of said cathode in accordance with variations in the discharge current in order to maintain the discharge current in said device constant,

9. In an electrical circuit the combination of a thermionic discharge device provided with an electron emitting cathode and subject to variations in discharge currents, a high-tension circuit including a high-tension transformer for energizing said device, a low-tension circuit including a low-tension transformer for heating the cathode of said device, a tertiary winding wound upon the core of said high-tension transformer and inductively coupled with said-first mentioned circuit, a tertiary winding diiferentially wound upon the core of said low-tension transformer and inductively coupled to said last mentioned circuit, and a circuit including both of said tertiary windings for causing variations in one of said circuits conversely to variations in the other of said circuits for maintaining the discharge current of said device constant.

MONTFORD MORRISON.

the primary winding of 

